Rhododendron plant named &#39;Holden52&#39;

ABSTRACT

A new and distinct Rhododendron cultivar named ‘HOLDEN52’ is disclosed, characterized by colorful rose-pink flowers with definite white and light pink patterning. Plants are heat tolerant to USDA zone 9 and cold hardy to Zone 5. Resistance to Phytophthora root rot has been observed. Plants have a dense, mounded habit and dark green, glossy mature foliage. The new cultivar is a Rhododendron, suitable for ornamental garden purposes.

Latin name of the genus and species: Rhododendron hybrida.

Variety denomination: ‘HOLDEN52’.

BACKGROUND OF THE INVENTION

The new cultivar is a product of a planned breeding program. This newvariety, hereinafter referred to as ‘HOLDEN52’, was discovered as aseedling, resulting from the crossing of an unpatented, unnamedRhododendron hyperthyrum with the pollen parent Rhododendron hybrida‘Henry's Red’, unpatented. The cross resulting in the new varietyoccurred during 2005. The new variety was selected by the inventorduring of 2010 at an arboretum in Madison, Ohio.

After identifying the new variety as a potentially interestingselection, the inventor first organized propagation of ‘HOLDEN52’ byvegetative cuttings Fall of 2007 at the same arboretum in Madison, Ohio.The inventor continued controlled testing and propagation, assessingstability of the unique characteristics of this variety. Multiplegenerations have been reproduced and have shown that the unique featuresof this cultivar are stable and reproduced true to type.

SUMMARY OF THE INVENTION

The cultivar ‘HOLDEN52’ has not been observed under all possibleenvironmental conditions. The phenotype may vary somewhat withvariations in environment such as temperature, day length, and lightintensity, without, however, any variance in genotype. The followingtraits have been repeatedly observed and are determined to be the uniquecharacteristics of ‘HOLDEN52’ These characteristics in combinationdistinguish ‘HOLDEN52’ as a new and distinct Rhododendron cultivar:

-   -   1. Colorful rose-pink flowers with definite white and light pink        patterning and dark red speckles located on the central upper        petal.    -   2. Dark green, glossy foliage and a dense, mounded habit.    -   3. Heat tolerant (USDA hardiness zone 9) in open field tests        (Louisiana).    -   4. Cold hardy (USDA hardiness zone 5) in open field tests        (Ohio).    -   5. Resistant to Phytophthora root rot.

COMPARISON TO PARENT VARIETY

‘HOLDEN52’ is similar in most horticultural characteristics to the seedparent, however, plants of the new cultivar ‘HOLDEN52’ however differ inthe following:

-   -   1. The new variety has pink patterned flowers, the seed parent        has white flowers.    -   2. The new variety is more cold hardy than the seed parent.    -   3. Inflorescence (trust) of the new variety has a pyramidal        configuration, compared to the open, floppy inflorescence of the        seed parent variety.

‘HOLDEN52’ is similar in most horticultural characteristics to thepollen parent, however plants of the new cultivar ‘HOLDEN52’ howeverdiffer in the following:

-   -   1. ‘HOLDEN52’ produces pink flowers, the pollen parent produces        burgundy red flowers.    -   2. The new variety tolerates more heat than the pollen parent.    -   3. The new variety is Phytophthora root rot resistant, the        pollen parent is not.

COMMERCIAL COMPARISON

‘HOLDEN52’ can be compared to the commercial variety Rhododendron hybrid‘Dandyman Pink’, unpatented. Plants of the new cultivar ‘HOLDEN52’ aresimilar to plants of ‘Dandyman Pink’ in most horticulturalcharacteristics, however, plants of the new cultivar ‘HOLDEN52’ differin the following:

-   -   1. Flowers of ‘Holden52’ have a stronger, more definite and        contrasting color pattern than ‘Dandyman Pink’.    -   2. Foliage of ‘Holden52’ is darker green and lacks the leaf        twisting seen in ‘Dandyman Pink’.

‘HOLDEN52’ can be compared to the commercial variety Rhododendron hybrid‘Peppermint Twist’, unpatented. Plants of the new cultivar ‘HOLDEN52’are similar to plants of ‘Peppermint Twist’ in most horticulturalcharacteristics, however, plants of the new cultivar ‘HOLDEN52’ differin the following:

-   -   1. Flowers of ‘Holden52’ have a stronger, more definite and        contrasting color pattern than ‘Peppermint Twist’, as well as a        deeper pink color.    -   2. Foliage of ‘Holden52’ is darker green and more glossy.    -   3. Plant habit of the new variety is more mounded and dense        compared to the open, upright habit of ‘Peppermint Twist’.    -   4. The new variety is observed to be somewhat more cold hardy        than ‘Peppermint Twist’.

BRIEF DESCRIPTION OF THE PHOTOGRAPHS

The accompanying photograph in FIG. 1 illustrates in full color atypical plant of ‘Holden52’ in the ground at approximately 3 years ofage.

FIG. 2 illustrates a close up of a typical inflorescence of the newvariety.

The photographs were taken using conventional techniques and althoughcolors may appear different from actual colors due to light reflectanceit is as accurate as possible by conventional photographic techniques.

DETAILED BOTANICAL DESCRIPTION

In the following description, color references are made to The RoyalHorticultural Society Colour Chart 2007 except where general terms ofordinary dictionary significance are used. The following observationsand measurements describe ‘HOLDEN52’ plants grown outdoors in Loxley,Ala. Plants are approximately 2 years old, in a 3 gallon nurserycontainer. Measurements and numerical values represent averages oftypical plant types.

-   Botanical classification: Rhododendron hybrida ‘HOLDEN52’.

PROPAGATION

-   Typically by semi-hardwood cuttings in Spring and Summer.-   Root description: Fine, fibrous young roots, well branched. Colored    near RHS Brown 200D.

PLANT

-   Growth habit: Mounded globular evergreen shrub.-   Height: Approximately 45 cm to top of foliar and flowering plane.-   Growth rate: Rapid.-   Plant spread: Approximately 55 cm.-   Branching characteristics: About 2 to 4 primary branches from the    center of the plant. Branches occur at approximately 35° to 75°    angles. Each primary branch has 2 to 4 lateral branches.-   Primary branches:-   Length of primary branches: Average 20 cm.-   Diameter of primary branches: Approximately 0.8 cm.-   Primary branch strength: Very strong and difficult to break.-   Primary branch color: Young primary branches near RHS Yellow-Green    144C; oldest branches become woody, colored near Brown 200B.-   Primary branch texture: Older growth scaly, hirsute.-   Lateral branches:-   Number of lateral branches: Approximately 2 to 4 per primary branch.-   Length of lateral branches: Average 12 cm.-   Diameter of lateral branches: Average 0.7 cm.-   Lateral branch strength: Very strong, flexible.-   Lateral branch color: Immature branches near RHS Greyed-Red 180A,    turning, Yellow-Green 144C.-   Lateral branch texture: Hirsute.-   Internode length: Average 2.0 to 2.5 cm.-   Age of plant described: Approximately 2 years.

FOLIAGE

-   Leaf:    -   -   Type.—Simple.        -   Arrangement.—Alternate.        -   Average length.—Average range 6.5 to 10.8 cm.        -   Average width.—Average range 3.1 to 3.7 cm.        -   Shape of blade.—Obovate.        -   Apex.—Shallow mucronate.        -   Base.—Broad attenuate.        -   Attachment.—Stalked.        -   Margin.—Entire.        -   Texture of top surface.—Glabrous.        -   Texture of bottom surface.—Glabrous.        -   Appearance top surface.—Mature foliage glossy. Young foliage            matte.        -   Appearance bottom surface.—Matte.        -   Aspect.—Concave to somewhat concave.        -   Color.—Young foliage upper side: Near RHS Green 143B. Young            foliage under side: Near RHS Green 143C. Mature foliage            upper side: Near RHS Green 139A. Mature foliage under side:            Near RHS Green 137D.        -   Venation.—Type: Pinnate. Venation color upper side: Near RHS            Yellow-Green N144B. Venation color under side: Near RHS            Yellow-Green N144D.        -   Petiole.—Length: About 1.0 cm. Diameter: About 0.3 cm.            Color: Upper Surface: Near RHS Yellow-Green N144A. Lower            Surface: Near RHS Yellow-Green N144B.

FLOWER

-   Bloom period: Spring.-   Flower:-   Arrangement: Axillary clusters of single, perfect, open funnel    shaped individual flowers. Typically 10 to 15 flowers per cluster.-   Inflorescence:    -   -   Height.—Average 14.0 cm.        -   Diameter.—Average 10.0 cm.-   Peduncle:    -   -   Length.—Average range 3 to 6 cm.        -   Diameter.—0.8 cm.        -   Color.—Near RHS Yellow-Green 144C.        -   Texture.—Glabrous.        -   Aspect.—Straight. Angle of attachment, approximately 15°            angle from stem.-   Flowers:    -   -   Length.—Average 6.8 cm.        -   Diameter.—Average 5.7 cm.        -   Facing direction.—Outwardly facing.        -   Persistent or self-cleaning.—Petals self-cleaning.        -   Fragrance.—Very faint.-   Tube:    -   -   Tube length.—Approximately 2.3 cm.        -   Tube width a widest point.—Approximately 1.9 cm.        -   Tube width and narrowest point.—Approximately 0.6 cm.-   Petals:    -   -   Unfused petal segments.—.        -   Length.—Approximately 4.7 cm.        -   Width.—Approximately 2.9 cm.        -   Apex.—Rounded.        -   Shape of petal.—Unfused portion, obovate to broad, rounded            deltate.        -   Petal margin.—Entire. Aspect very slightly undulating.        -   Petal arrangement.—Overlapping, bilateral symmetry            dissecting bottom petal. Petals fused approximately ⅓ fused            from base.        -   Petal number.—5.        -   Petal texture.—Smooth.-   Color:    -   -   Upper surface at first opening.—Near RHS Red 54B flushed            53D, 55D at base. Uppermost central petal has linear            speckles colored near Red 53D.        -   Under surface at first opening.—Near RHS Red 52B.        -   Inner surface at maturity.—Near RHS Red 54B flushed 53D,            Red-Purple 62D. Central streak near White N155B. Uppermost            central petal has linear speckles colored near Red 53D.        -   Outer surface at maturity.—Near RHS Red 54B, lower section            Red 56A, center streak near Red-Purple 62D.        -   Upper surface at fading.—Main surface near Red-Purple 62D,            apex and margin near 55C. Uppermost central petal has linear            speckles colored near Red 53D.        -   Under surface at fading.—Main surface near Red 55D, flushed            Red-Purple 62C and 62B.-   Bud:    -   -   Shape.—Elliptic.        -   Length.—4.1 cm.        -   Diameter.—2.4 cm.        -   Color.—Near RHS Red 54B, flushed 53D.-   Calyx/sepals:    -   -   Quantity per flower.—5 sepals.        -   Shape.—Narrow deltate.        -   Length.—1.4 cm.        -   Width.—0.8 cm.        -   Apex.—Acute.        -   Base.—Fused.        -   Margin.—Entire.        -   Texture.—Highly pubescent. Color: Inner Surface: Near RHS            Yellow-Green 145A. Outer Surface: Near RHS Yellow-Green            145A.

REPRODUCTIVE ORGANS

-   Stamens:    -   -   Number.—5.        -   Length.—3.4 cm.        -   Width.—0.1 cm.        -   Color.—Near RHS Red 56D.        -   Anthers.—Length: Approximately 0.3 cm. Color: Near RHS            Yellow-Green 154D. Pollen: Not observed.-   Pistil:    -   -   Number.—1.        -   Length.—5.3 cm.        -   Style.—Length: Average 4.4 cm. Color: Near RHS Red 56D.        -   Stigma.—Globular, colored near 53A.        -   Ovary.—Sericeous texture. Approximately 0.4 cm in diameter.            Colored near Yellow-Green 145A.

OTHER CHARACTERISTICS

-   Disease and pest resistance: Resistance to Phytophthora root rot has    been observed. Not observed to be susceptible nor resistant to other    normal diseases and pests of Rhododendron.-   Temperature tolerance: USDA Zone 6 though Zone 9.-   Fruit/seed production: Not observed to date.

What is claimed is:
 1. A new and distinct cultivar of Rhododendron plantnamed ‘HOLDEN52’ as herein illustrated and described.